Art of burning finely-divided fuel for the generation of steam



July 22, 1930. E. LUNDGREN ART OF BURNING FINELY DIVIDED FUEL FOR THE GENERATION OF STEAM Filed March 26, 1925 2 Sheets-Sheet 1 IN VEN TOR T ATTORNEYS LUNDGRE N 1,770,987

' ART OF BURNING FINELY DIVIDEID FUEL FOR THE GENERATION. OF STEAM July 22, 1930.

2 Sheets-Sheet 2 INVENTOR ATTOR EYS Patented July 22, 1930 v UNITED STATES PATENT OFFICE EDWIN-LUNFGREN, OF ZERFDEIR IIIGK, MARYLAND, ASSIGNOR TO COMBUSTION ENGI- NEEBING 'CORPORATION, A CORPORATION OF NEW YORK .AiRT OF BURNING- FINELY-DIVIDED FUEL FOR THE GENERATION OF STEAM Application filed March 26, 1925. Serial No. 18,338.

Thisspecification relates to the art of burn ing finely divided fuel in suspension, particularly pulverized coal, for the generation of steam;

In some aspects the invention has to do with combustion, in others with the boiler,

and in still others With a combination involv-- ing both.

Among other objects and advantages, etc., I

The invention provides a rational design of pulverized fuel boiler in which the .fuel burning as Well as boiler design have been considered in respect to each other.

The radiant heat from the burning coal particles as well as from the gases is utilized to a greater extent than heretofore known.

The large expensive furnaces heretofore buig. of refractory material are dispensed wit A combustion space is provided within the boiler proper in order to eliminate the expensive furnaces'heretofore used and the high maintenance incident to the same, and to decrease the space requirement.

An improved boiler design is provided,

having a water screen for cooling of the ash as an integral part of the boiler.

Improved means and manner of feeding and burningthe fuel are contemplated, inter alia, by means of highly preheated air, and independent control of the volume and pressure of the primary air and secondary air used for combustion; i. e., the combustion and boiler are correlated.

4 More specifically, combustion, economy and efficiency are furthered by enclosing. the fuel and primary air between two sheets of high velocity highly heated air to secure a hot flame and to prevent the finer particles of fuel from the burner, from being short circuited into the bank of boiler tubes withoutcomplete burning; and

By providing a method of firing pulverized fuel by injecting it downwardly, sub stantially in a vertical direction and forming two U shaped flames, the upgoing gases in each leg of the U being utilized for heating and assisting the combustion of the descending fuel and air mixture; and

By providing a combustion chamber having substantially the shape of a vertical section of a truncated cone, with means to admit fuel and air in the upper portion of the combustion chamber and means to form a double U-ilhaped flame in the combustion space; an

By providing such a combustion chamber formed substantially of tube surfaces for' .other objects as may hereinafter appear, or

are incident to my invention, are realized, is illustrated in the accompanying drawings, wherein Figure 1 is a Vertical section through a boiler and furnace embodying the invention; and

Figure 2 is a section taken of'Figure 1.

Referring to Fig. 1.-1, 2, 3 and 4: are the upper and lower drums respectively of a boiler unit having tubes 5, 6 and 7 between the upper and lower drums. A baffle 8 is located in the upper portion of tube bank 5 to prevent short c rcuiting of fine fuel through gas passage 9 and may enclose the outside of the outer tubes 5 to provide an ignition zone in the upper part of the combustion chamber 14. A baffle 10 divides tube banks 5 and 6 and similarly a baflie 11 divides tube banks 6 and 7. Circulatingtubes 12 connect the upper drums and circulating tubes 13 connect the on the line 2-2 lower drums and also form a screen for coolduct 18, fan 19 and its motor 20 which may be of the variable speed type to provide the necessary air volume and pressure. Fuel is admitted through supply bunker 21 into the feeder 16.

The gases leave the boiler atuptakes 22 and enter the air heaters 23, from there passing into the breeching 2a to the stack and atmosphere. Dampers 25 may be used to control the draft which may be created by a stack or induced draft fans.

A fan 26 forces the secondary combustion air through each distribution duct and air heater 23 from where the air enters the ducts 28 and, through connections 29,- passes to the second air heaters consisting of tubes 30. Fig. 2 shows the circuit of the secondary air and how it passes through the tubes 30 into ducts 31 to the distributin ducts 32 from which it enters the air supplying nozzles 33 also shown in Fig. 1.

It can thus be seen that the secondary air preheated in heaters 23 is heated to a high temperature in tubes 30, as the same are located in the relatively high temperature existing in tube bank 5. The location, as shown, of tubes 30, protects them however from the destructive temperature in the combustion chamber 14. The fuel stream supplied with its primary preheated air enters the combustion chamber through burners 15 between two sheets of highly preheated air admitted through nozzles 33. As described the volume and pressure of the primary air and the'sec ondary air can'be varied in relation to each other.

The fuel and air stream will descend due to gravity and injection pressure until it loses its velocity and turns upwards in two streams due to the draft through the furnace and boiler passes, in the meantime burning, and receiving additional combustion air from the highly heated air injected through nozzles 33. The two rising gas streams through radiation and contact facilitate the combustion of the descending fuel stream.

Due to the reversal of direction of the gas stream and relative low velocity at its burning point the ash formed passes downward between the circulating tubes 13 which are spaced apart for this purpose, and is deposited in ash hopper 34 and ultimately disposed of through opening and gate 35. The screen 13 is between the combustion space and the ash hopper.

Evaporating tubes 36 may be used in the side walls of the combustion chamber.

From the foregoing it will be seen that the fuel sheet first enters a comparatively restricted ignition zone defined by refractory material radiating heat, the fuel being thereby ignited, sufficient air for this purpose being carried with the coal. Prompt ignition and early thorough establishment of combustion cross-section to accommodate the increasing volume of the fuel, flame and gas stream. In traveling downwardly, the fuel and flame stream is subjected to sheets of preheated secondary air, directed, referably at high velocity, so as to prevent s iort-circuiting, promote admixture and hasten combustion. A short hot flame is produced and this coupled with the fact that the combustion air is preheated overcomes the chilling effect of the radiant heat boiler tubes which would otherwise be detriment-a1 to complete combustion and efiiciency. Since the combustion space is largely defined by boiler tubes subject to radiant heat, the capacity is greatly increased, while at the same time the size not only of the boiler, but also of the whole setting may be quite small in comparison to standard practice.

By the independent control of the offtakes, the flame may be caused to divide equally.

The burners 15 and the nozzles 33 are flat-T tenedto deliver the sheets of fuel and air respectively.

I claim: I

1. In combination, a combustion chamber, and means for admitting finely divided fuel downwardly in the upper part of the chamber approximately centrally thereof, said chamber having offtakes located so as to cause the fuel and flame stream to divide in approximately double U form.

2. In combination, a combustion chamber,

and means for admitting finely divided fuel downwardly in-the upper part of the cham ber approximately centrally thereof, said chamber having offtakes located so as to cause the fuel and flame stream to divide in approximately double U form, together with means for admitting downwardly directed streams of air on opposite sides of the entering fuelstream.

3. In combination, a combustion chamber,

and means for admitting finely divided fuel downwardly in the upper part of the chamber approximately centrally thereof, said chamber having ott'takes located so as to cause the fuel and flame stream to divide in approximately double U form,together with means for admitting downwardly directed streams of air, on opposite sides of theentering fuel stream, said air being preheated.

4. In combination, a combustion chamber, and means for admitting finely divided fuel downwardly in the upper part of the chamber approximately centrally thereof, said chamber having oiftakes located so as to cause the fuel and flame stream to divide in approximately double U form, said chamber having refractories defining the upper portion of the combustion space and having circulating tubes defining lower combustion space.

5. The process of burning pulverized coal in a combustion chamber having combustion space thereof defined by circulatory tubes subject to radiant heat, which consists in centrally admitting the fuel in a downward direction at the upper part of the chamber, in burning the fuel with a relatively short hot flame, and in causing the fuel and flame stream to divide in double U-form.

6. The process of burning pulverized coal in a combustion chamber having, combustion .space thereof defined by circulatory tubes subject to radiant heat, which consists in centrally admitting the fuel in a downward direction at the upper part of the chamber, in violently mixing the fuel and air, and in causing the fuel and, flame stream to divide in double U-form.

7. The process of burning pulverized coal in a combustion chamber having combustion space thereof defined by circulatory tubes subject to radiant heat, Which consists in centrally admitting the fuel in a downward direction at the upper part of the chamber, in violently mixing the fuel and preheated air, and in causing the fuel and flame stream to divide in double U-form.

In testimony whereof, I have hereunto signed my name. EDWIN LUNDGREN. 

